New 4Runner, bad exhaust Valve, what to do

Hi I just bought my first 4Runner. A 1999 white 3rz standard. Got it for really cheap because of engine problems. Did a compression test and 1 cylinder is at 75 psi, the rest are around 175 psi. I did a leak down test and it's flying out the exhaust pipe. My question is should i just replace the one shot valve or rebuild the whole head. If I do, what do i need replace and what doesn't. Not sitting on bags of moneys but if i need to I'll pull out of saving to do the work i will. Thanks for the help?

 

Well you're going to pull the head anyway to replace that bad valve. Once you've done so, you can check the condition of the rest to make the go no-go decision. Had this been my vehicle, I'd opt for a complete rebuilt head assuming of course that the rest of the vehicle is OK

 

While I have the head out, is there anything else I should be replacing besides the valves? The rest of the car is tip top.

 

If it were mine I would do a complete valve job, perhaps the good valves just need a touching up.

 

Sounds like a plan! I'll replace what I need to and clean up what i can. Any other recommendations while I have the head out? Thanks for the input!

 

I'm not up on the 3rz, but have done a bunch of valve jobs, I'm not to much help on this engine. Sorry. Some one here knows.

 

Of course replacing the valves is not sufficient. You'll need to to re-seat them. And if I am replacing the valves, I'll be replacing the guides as well the cam followers. Given this I'm more inclined to buy a rebuilt head from a reputable place just because I don't trust myself in rebuilding a head.

 

Thanks Matt!

 

Here's that bad valve..

My intake manifold is very wet and dirty. Does anyone know the cause?

 

Thanks for posting this picture. Since you have a cracked intake valve, you were either not getting any combustion or perhaps a incomplete one in that cylinder. Every time the cylinder came up, I surmise it forced some of the fuel/air/exhaust mixture back into the intake. My curiosity is more on the valve. Why would the intake valve crack? Worn valve guide? We also do not know about the rest of the head so this is where a shop can test it out for you.

 

The cracked one is the exhaust valve. I know there is a crack in the exhaust manifold. Not sure if that can cause a valve to go bad. I have no experience in that issue.

The rest of the valves look good, just a little dirty. I cleaned them up a bit. Need a special tool to take the valves out and lap. Need to find our rent the adaptor.

 

My mistake. Should have noted it is exhaust by its color and smaller size. Now I am on the same page as you were. Why would intake be so affected? Perhaps there is another damage that we're seeing and that is where a shop can help. Nice cleaning job by the way.

An after thought. During the intake cycle as the cylinder moves down, it creates suction which then brings in fresh air/fuel through the intake valve. Given the crack in the exhaust valve the suction capability would be impacted and perhaps only a fraction of the mixture made it in and the rest remained in the intake

 

I was don't some research and a lot of 4Runner owners talk about installing an oil catch can. Is that something I need to do in the future? Maybe that's why the intake is so wet.

 

Maybe your EGR valve is bad, that may or may not be another reason for the 'wet' in the intake. That exhaust valve just didn't decide to go bad, I would suspect getting 'rode hard and put away wet' was the start of the problem. If you were stuck or in a situation where the vehicle temp was on the verge of overheating or the like, then shut off the engine without a cool down period that could have cracked that valve and started this process of 'burning the valve, you mentioned cracked exhaust manifold, same process except cool air seeps in upon shut off and cracks the valve. One other thing that could have burned that valve would be improper valve lash, then over a period of time it cracked. So it doesn't really matter "what came first ? the burn or the crack." Just giving you some 'suggestions' on why this may have happened. How's it going fixing it? P.S.- don't forget to check valve guides, if they are sloppy, get "em changed!

 

Should not hurt having one. However if there is a underlying issue with the engine, you want to fix that as opposed to treating the symptoms with an oil catch can.

 

"My intake manifold is very wet and dirty. Does anyone know the cause?"

The crack in the exhaust manifold would cause rapid cool down and was most likely the culprit of the cracked valve. imo

The cracked exhaust valve is not allowing complete cylinder combustion. Hence the build up in the head and perhaps, back stream too(intake).

You should have the head die tested for cracks and checked to see if it needs to be resurfaced(milled). Over the long haul damage like this can have numerous reasons. One is, shutting the engine down when it's in the high range of it's heat cycle(or a cracked header). The pro's say it's best to let an engine idle for a minute or so before turning it off. Like we have time for that.

 

Answer is simple= cracked exhaust manifold created a lean condition on that cylinder and burnt the valve...,
Sounds funny but exhaust gases actually cool the combustion chamber.

 

Thanks for all the advice! I'm in the process of removing the valves to replace or lap. But the spring compressor I have wont work with the bucket shims. So I bought one off Amazon that says it works for my car but it doesn't. Dose anyone know how to go about this? Did I miss a step or is it just the wrong tool?

 

Excuse my ignorance... They just pull out. Sorry.. I'll update when on the next step.

 

I rigged my old spring compressor to fit the attachment from this cheap Amazon compressor (it sucks). Also put duck tape around it so i don't damage the aluminum. So far it's working perfectly.



Besides the crack in the valve everything looks good. I am a noob at this so any tips and advise is appreciate. Thanks 4Runner gang, back to work!

 

Titanium replacements would be nice...

 

They are available. Probably about $1,000 - $1200 for the set, then there's the lead time on making them.

 

Kinda off topic but, my Wife was walking behind me and noticed that you’re using a fabric cutting mat. And she said that for your sake and well being that you are using an old one.
Is your partner a quilter?

 

I bought that from a auction. I thought it was just a regular cutting mat lol thanks for letting me know!

 

That's too rich for my blood, thanks though!

 

Why would that lean out 1 chamber? Doesn't make sense at all

 

So logically thinking out loud...

A cracked exhaust manifold would allow gas to escape before the downstream sensors?

Which would cause the ECU to compensate?

Which would cause richening of the fuel mix?

Discuss?

 

I was thinking that as well. The crack was right in the middle of the manifold. You would think cylinders 2 and 3 would be most affected from the "cooling".

 

Would that explain the wetness in the intake manifold as well?

 

You would think that naturally I know. It’s OK. Actually any escaping exhaust creates a lean condition...